US10553734B2 - Semiconductor device and manufacturing method thereof - Google Patents
Semiconductor device and manufacturing method thereof Download PDFInfo
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- US10553734B2 US10553734B2 US15/980,661 US201815980661A US10553734B2 US 10553734 B2 US10553734 B2 US 10553734B2 US 201815980661 A US201815980661 A US 201815980661A US 10553734 B2 US10553734 B2 US 10553734B2
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Images
Classifications
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- G—PHYSICS
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- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/13—Integrated optical circuits characterised by the manufacturing method
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0232—Optical elements or arrangements associated with the device
- H01L31/02327—Optical elements or arrangements associated with the device the optical elements being integrated or being directly associated to the device, e.g. back reflectors
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/43—Arrangements comprising a plurality of opto-electronic elements and associated optical interconnections
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- G—PHYSICS
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/015—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements with at least one potential jump barrier, e.g. PN, PIN junction
- G02F1/025—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements with at least one potential jump barrier, e.g. PN, PIN junction in an optical waveguide structure
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/02002—Arrangements for conducting electric current to or from the device in operations
- H01L31/02005—Arrangements for conducting electric current to or from the device in operations for device characterised by at least one potential jump barrier or surface barrier
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/024—Arrangements for cooling, heating, ventilating or temperature compensation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
- H01L31/0264—Inorganic materials
- H01L31/028—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic System
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
- H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by at least one potential-jump barrier or surface barrier, e.g. phototransistors
- H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
- H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier or surface barrier
- H01L31/109—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier or surface barrier the potential barrier being of the PN heterojunction type
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic System
- H01L31/1808—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic System including only Ge
Definitions
- the present invention relates to a semiconductor device and a manufacturing method thereof, and can be used appropriately for a semiconductor device in which, e.g., a silicon photonics device is embedded and a manufacturing method thereof.
- the silicon photonics technique couples an optical device and an electronic device to each other via an optical circuit using an optical waveguide made of silicon used as a material.
- a semiconductor device in which an optical device and an electronic device are thus coupled to each other using an optical circuit and mounted is referred to as an optical communication module.
- Such semiconductor devices include a semiconductor device having, as a transmission line for an optical signal, an optical waveguide made of a semiconductor layer formed over a base via an insulating layer and an insulating film formed such that the insulating film covers the optical waveguide.
- the optical waveguide functions as a core layer, while the insulating layer and the insulating film function as a clad layer.
- FIG. 1 shows a cross-sectional view of a silicon photonics platform having a germanium photodetector (Ge PD), a Si modulator (Si MOD), a Si waveguide (Si WG), and a TiN heater.
- Ge PD germanium photodetector
- Si MOD Si modulator
- Si WG Si waveguide
- TiN heater TiN heater
- Non-Patent Document 1 Andy Eu-Jin Lim et al., “Review of Silicon Photonics Foundry Efforts”, IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 20, NO. 4, JULY/AUGUST 2014, 8300112
- the present inventors have been considering embedding an optical modulator and an optical receiver (photoelectric converter) in a semiconductor device to which a silicon photonics technique is applied and using heating involving the use of a heater for the optical modulator. In this case, it is necessary to couple various elements to wires, but the reliability of the semiconductor device deteriorates unless a coupling structure therefor is inventively improved.
- a semiconductor device includes an insulating layer formed over a base, a first optical waveguide and a first semiconductor portion which are formed over the insulating layer, a second semiconductor portion formed over the first semiconductor portion, and a first interlayer insulating film formed over the insulating layer such that the first interlayer insulating film covers the first optical waveguide, the first semiconductor portion, and the second semiconductor portion.
- a first opening reaching the first semiconductor portion and a second opening reaching the second semiconductor portion are formed.
- the semiconductor device further includes a first coupling electrode formed continuously in the first opening and over the first interlayer insulating film and electrically coupled with the first semiconductor portion, a second coupling electrode formed continuously in the second opening and over the first interlayer insulating film and electrically coupled with the second semiconductor portion, and a heater portion formed over the first interlayer insulating film and over the first optical waveguide.
- a second interlayer insulating film is formed such that the second interlayer insulating film covers the heater portion, the first coupling electrode, and the second coupling electrode.
- a first wire formed over the second interlayer insulating film is electrically coupled with the heater portion via a first conductive plug embedded in the second interlayer insulating film.
- a second wire formed over the second interlayer insulating film is electrically coupled with the first coupling electrode via a second conductive plug embedded in the second interlayer insulating film.
- a third wire formed over the second interlayer insulating film is electrically coupled with the second coupling electrode via a third conductive plug embedded in the second interlayer insulating film.
- FIG. 1 is a schematic diagram showing an example of a configuration of an optical communication module according to an embodiment
- FIG. 2 is a main-portion cross-sectional view showing the semiconductor device in the embodiment
- FIG. 3 is a main-portion plan view of the semiconductor device in the embodiment.
- FIG. 4 is a main-portion plan view of the semiconductor device in the embodiment.
- FIG. 5 is a main-portion plan view of the semiconductor device in the embodiment.
- FIG. 6 is a main-portion plan view of the semiconductor device in the embodiment.
- FIG. 7 is a main-portion plan view of the semiconductor device in the embodiment.
- FIG. 8 is a main-portion plan view of the semiconductor device in the embodiment.
- FIG. 9 is a main-portion plan view of the semiconductor device in the embodiment.
- FIG. 10 is a main-portion cross-sectional view of the semiconductor device in the embodiment during the manufacturing process thereof;
- FIG. 11 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 10 ;
- FIG. 12 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 11 ;
- FIG. 13 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 12 ;
- FIG. 14 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 13 ;
- FIG. 15 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 14 ;
- FIG. 16 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 15 ;
- FIG. 17 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 16 ;
- FIG. 18 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 17 ;
- FIG. 19 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 18 ;
- FIG. 20 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 19 ;
- FIG. 21 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 20 ;
- FIG. 22 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 21 ;
- FIG. 23 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 22 ;
- FIG. 24 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 23 ;
- FIG. 25 is a main-portion cross-sectional view of a semiconductor device in a studied example
- FIG. 26 is a main-portion cross-sectional view of the semiconductor device in the studied example during the manufacturing process thereof;
- FIG. 27 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 26 ;
- FIG. 28 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 27 ;
- FIG. 29 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 28 ;
- FIG. 30 is a main-portion cross-sectional view of the semiconductor device during the manufacturing process thereof, which is subsequent to FIG. 29 ;
- FIG. 31 is a main-portion cross-sectional view showing a semiconductor device in another embodiment
- FIG. 32 is a main-portion plan view of the semiconductor device in the other embodiment.
- FIG. 33 is a main-portion plan view of the semiconductor device in the other embodiment.
- hatching may be omitted even from a cross-sectional view for improved clarity of illustration.
- a plan view may be hatched for improved clarity of illustration.
- FIG. 1 is a schematic diagram showing the example of the configuration of the optical communication module according to the present first embodiment.
- the arrows hatched with dots show the flow of an electric signal, while the non-hatched arrows show the flow of an optical signal.
- data output from a silicon electronic circuit C 1 in which, e.g., a control circuit, a memory circuit, or the like is formed is transmitted as an electric signal to an optical modulator P 1 via a silicon electronic circuit (transceiver IC) C 2 .
- the optical modulator P 1 is an optical device which converts the data transmitted as the electric signal to an optical signal.
- On the optical modulator P 1 e.g., a continuous wave laser beam from a light source LS is incident. By controlling the phase of the beam in the optical modulator P 1 and thus changing the state of the optical signal, it is possible to associate the data transmitted as the electric signal with the phase state of the beam.
- the optical signal resulting from the modulation in the optical modulator P 1 is output from the optical communication module (semiconductor device) SD to the outside via an optical coupler P 2 such as, e.g., a grating coupler or a spot size converter.
- an optical coupler P 2 such as, e.g., a grating coupler or a spot size converter.
- the optical signal input to the optical communication module (semiconductor device) SD is transmitted to an optical receiver P 4 via an optical coupler P 3 such as, e.g., a grating coupler or a spot size converter.
- the optical receiver P 4 is an optical device which converts the data transmitted as the optical signal to an electric signal.
- the data converted to the electric signal in the optical receiver P 4 is transmitted to the silicon electronic circuit C 1 via a silicon electronic circuit (receiver IC) C 3 .
- an electric wire made mainly of a conductive material such as aluminum (Al), copper (Cu), or tungsten (W) is used.
- a transmission line for an optical signal (hereinafter referred to as an optical signal line) made of, e.g., silicon (Si) is used.
- An optical waveguide described later corresponds to the optical signal line.
- the silicon electronic circuit C 1 is formed in a semiconductor chip SC 1 .
- the silicon electronic circuit C 2 is formed in a semiconductor chip SC 2 .
- the silicon electronic circuit C 3 is formed in a semiconductor chip SC 3 .
- the optical modulator P 1 , the optical couplers P 2 and P 3 , and the optical receiver P 4 are formed in one semiconductor chip SC 4 .
- These semiconductor chips SC 1 , SC 2 , SC 3 , and SC 4 and the light source LS are mounted over, e.g., one interposer IP to form the optical communication module (semiconductor device) SD.
- the electronic device and the optical device which are used herein are formed in the different semiconductor chips, but the configuration is not limited thereto.
- the electronic device and the optical device can also be formed in one semiconductor chip.
- FIG. 2 is a main-portion cross-sectional view showing the semiconductor device in the present first embodiment.
- the semiconductor device shown in FIG. 2 corresponds to the semiconductor chip SC 4 in FIG. 1 described above.
- FIGS. 3 to 9 are main-portion plan views of the semiconductor device in the present first embodiment.
- FIG. 3 shows a plan view of an area AR 1 .
- FIGS. 4 and 5 show plan views of an area AR 2 .
- FIGS. 6 and 7 show plan views of an area AR 3 .
- FIGS. 8 and 9 show plan views of an area AR 4 .
- a cross-sectional view at a position along the line A 1 -A 1 in FIG. 3 corresponds to a cross section of the area AR 1 in FIG. 2 .
- a cross-sectional view at a position along the line A 2 -A 2 in FIG. 4 corresponds to a cross section of the area AR 2 in FIG. 2 .
- a cross-sectional view at a position along the line A 3 -A 3 in FIG. 6 corresponds to a cross section of the area AR 3 in FIG. 3 .
- a cross-sectional view at a position along the line A 4 -A 4 in FIG. 8 corresponds to a cross section of the area AR 4 in FIG. 2 .
- FIGS. 4 and 5 show the plan views of the same area but, in FIG. 4 , optical waveguides WO 2 and semiconductor portions NR and PR are shown by the solid lines, contact holes CT 1 and CT 2 are shown by the two-dot-dash lines, and contact portions CB 1 and CB 2 are shown by the broken lines.
- FIG. 5 the optical waveguides WO 2 , the contact portions CB 1 and CB 2 , and plugs PG 1 and PG 2 are shown by the solid lines, and wires M 1 a and M 1 b are shown by the two-dot-dash lines.
- FIGS. 6 and 7 show the plan views of the same area but, in FIG.
- FIGS. 8 and 9 show the plan views of the same area but, in FIG. 8 , an optical waveguide WO 4 , semiconductor portions PRO and NRO, and a cap layer CP are shown by the solid lines, contact holes CT 3 and CT 4 are shown by the two-dot-dash lines, and contact portions CB 3 and CB 4 are shown by the broken lines.
- FIG. 8 an optical waveguide WO 4 , semiconductor portions PRO and NRO, and a cap layer CP are shown by the solid lines, contact holes CT 3 and CT 4 are shown by the two-dot-dash lines, and contact portions CB 3 and CB 4 are shown by the broken lines.
- FIG. 8 an optical waveguide WO 4 , semiconductor portions PRO and NRO, and a cap layer CP are shown by the solid lines, contact holes CT 3 and CT 4 are shown by the two-dot-dash lines, and contact portions CB 3 and CB 4 are shown by the broken lines.
- FIG. 8 an optical waveguide WO 4 , semiconductor portions PRO and
- the optical waveguide WO 4 , the contact portions CB 3 and CB 4 , and plugs PG 3 and PG 4 are shown by the solid lines, and wires M 1 d and M 1 e are shown by the two-dot-dash lines.
- the semiconductor device in the present first embodiment includes a base (supporting substrate) SB 1 , an insulating layer CL formed over the base SB 1 , and a semiconductor layer SL formed over the insulating layer CL.
- the base SB 1 , the insulating layer CL, and the semiconductor layer SL form a SOI (Silicon on Insulator) substrate SB.
- the base SB 1 is a supporting substrate supporting the insulating layer CL and a structure above the insulating layer CL, which is a semiconductor substrate.
- the base SB 1 is preferably made of a monocrystalline silicon substrate, which is, e.g., a p-type monocrystalline silicon substrate having a (100) plane orientation and a specific resistance of about 5 to 50 ⁇ cm.
- the insulating layer CL is preferably made of a silicon oxide film.
- the insulating layer CL can also be regarded as a BOX (Buried Oxide) layer.
- the semiconductor layer SL is preferably made of a silicon layer (more specifically, a monocrystalline silicon layer) and can also be regarded as a SOI (Silicon on Insulator) layer.
- the SOI substrate SB has the area AR 1 , the area AR 2 , the area AR 3 , and the area AR 4 .
- the area AR 1 , the area AR 2 , the area AR 3 , and the area AR 4 correspond to the different two-dimensional areas of the main surface of the same SOI substrate SB.
- a transmission line for an optical signal (optical waveguide WO 1 ) is formed.
- an optical modulator (PC 1 ) is formed.
- an optical modulator (PC 2 ) is formed in the area AR 3 .
- an optical receiver germanium optical receiver PD
- FIG. 2 shows the areas AR 1 , AR 2 , AR 3 , and AR 4 which are sequentially adjacent to each other.
- the optical waveguide WO 1 as a transmission line for various optical signals is formed.
- the optical waveguide WO 1 is made of the semiconductor layer SL (silicon layer) and formed over the insulating layer CL.
- the lower surface of the optical waveguide WO 1 is in contact with the upper surface of the insulating layer CL.
- no impurity ion is implanted.
- the optical waveguide WO 1 is made of an intrinsic semiconductor, i.e., an i (intrinsic) type semiconductor.
- the optical waveguide WO 1 has a linear pattern extending in an X-direction.
- optical signal introduced into the optical waveguide WO 1 travels in the optical waveguide WO 1 along the extending direction of the optical waveguide WO 1 , which applies also to each of optical waveguides WO 2 , WO 3 , and WO 4 described later.
- X-direction and a Y-direction which are shown in FIGS. 3 to 9 are orthogonal to each other and are also generally parallel with the main surface of the SOI substrate SB (or with the main surface of the base SB 1 ).
- a direction perpendicular to the paper surface with FIG. 2 corresponds to the X-direction.
- an interlayer insulating film IL 3 is formed such that the interlayer insulating film IL 3 covers the optical waveguide WO 1 .
- the interlayer insulating film IL 3 is made of silicon oxide.
- the interlayer insulating film IL 3 is made of a multi-layer film including an insulating film IL 1 and an insulating film IL 2 over the insulating film IL 1 .
- each of the insulating film IL 1 and the insulating film IL 2 is made of a silicon oxide film.
- the insulating film IL 1 is in a lower layer and the insulating film IL 2 is in an upper layer, the insulating film IL 1 is in contact with the optical waveguide WO 1 .
- the optical waveguide WO 1 is surrounded circumferentially (from upper and lower sides and from left and right sides) by the insulating layer CL and the interlayer insulating film IL 3 (more specifically, the insulating film IL 1 ).
- the optical waveguide WO 1 can function as a core layer, while the insulating layer CL and the interlayer insulating film IL 3 can function as a clad layer.
- the refractive indices of the insulating layer CL and the interlayer insulating film IL 3 which serve as the clad layer are lower than the refractive indices of the optical waveguide WO 1 and the optical waveguides WO 2 and WO 3 described later.
- FIG. 2 shows the optical waveguide WO 1 having a quadrilateral (rectangular) cross-sectional shape.
- a grating coupler is also formed, though not shown in FIG. 2 .
- the grating coupler is also made of the semiconductor layer SL formed over the insulating layer CL and covered with the interlayer insulating film IL 3 .
- the grating coupler is equivalent to the foregoing optical couplers P 2 and P 3 .
- an interlayer insulating film IL 4 is formed over the interlayer insulating film IL 3 .
- wires M 1 are formed as necessary.
- the wires M 1 are the first-layer wires.
- the optical modulator PC 1 formed in the area AR 2 .
- the optical modulator PC 1 is formed in the area AR 2 .
- the optical modulator PC 1 corresponds to the foregoing optical modulator P 1 in FIG. 1 described above.
- the optical waveguide WO 2 extending in the X-direction is divided at a branch portion into the two optical waveguides WO 2 (i.e., an optical waveguide WO 2 a and an optical waveguide WO 2 b ).
- the two optical waveguides WO 2 extend in the X-direction, while being spaced apart from each other in the Y-direction, and are then reunited to form the one optical waveguide WO 2 extending in the X-direction.
- a phase modulation portion PM 1 is provided in each of the two optical waveguides WO 2 a and WO 2 b .
- the phase modulation portion PM 1 is an element which changes the phase of a light beam.
- the phase modulation portion PM 1 provided in the optical waveguide WO 2 a is referred to herein as a phase modulation portion PM 1 a
- the phase modulation portion PM 1 provided in the optical waveguide WO 2 b is referred to herein as a phase modulation portion PM 1 b
- the structure of the phase modulation portion PM 1 a and the structure of the phase modulation portion PM 1 b are basically the same.
- Each of the phase modulation portions PM 1 includes the optical waveguide WO 2 , the p-type semiconductor portion PR, and the n-type semiconductor portion NR.
- the optical waveguide WO 2 , the p-type semiconductor portion PR, and the n-type semiconductor portion NR are made of the semiconductor layer SL (silicon layer) and formed over the insulating layer CL.
- the respective lower surfaces of the optical waveguide WO 2 , the p-type semiconductor portion PR, and the n-type semiconductor portion NR are in contact with the upper surface of the insulating layer CL.
- the p-type semiconductor portion PR and the n-type semiconductor portion NR are formed integrally with the optical waveguide WO 2 (WO 2 a or WO 2 b ).
- the p-type semiconductor portion PR is provided while, on the other side thereof, the n-type semiconductor portion NR is provided.
- no impurity ion is implanted so that the optical waveguide WO 2 is made of an intrinsic semiconductor (i.e., an i-type region).
- a p-type impurity is introduced while, in the n-type semiconductor portion NR, an n-type impurity is introduced.
- the p-type semiconductor portion PR, the optical waveguide WO 2 , and the n-type semiconductor portion NR form an element with a pin structure (diode with a pin structure) and thus form the phase modulation portion PM 1 .
- the structure portion (PM 1 ) including the optical waveguide WO 2 , and the p-type semiconductor portion PR and the n-type semiconductor portion NR which are located on both sides thereof it is possible to change the phase of a light beam.
- a carrier density in the optical waveguide WO 2 (WO 2 a or WO 2 b ) made of an intrinsic semiconductor is changed to change the refractive index of the light beam in the optical waveguide WO 2 (WO 2 a or WO 2 b ).
- the wavelength of the light beam traveling in the optical waveguide WO 2 (WO 2 a or WO 2 b ) is changed to allow the phase of the light beam in the process of traveling in the optical waveguide WO 2 (WO 2 a or WO 2 b ) of the phase modulation portion PM 1 to be changed.
- the incident light beam from an input portion travels in the optical waveguide WO 2 and is divided at the branch portion into two light beams which travel in the two optical waveguides WO 2 a and WO 2 b .
- the two light beams have respective phases controlled in the respective phase modulation portions PM 1 provided in the optical waveguides WO 2 a and WO 2 b and are then reunited into one light beam which travels in the one optical waveguide WO 2 .
- the phase difference between the light beam that has passed through the optical waveguide WO 2 a of the phase modulation portion PM 1 a and the light beam that has passed through the optical waveguide WO 2 b of the phase modulation portion PM 1 b is adjusted to thus allow the phase and intensity of the light beam output from the optical modulators PC 1 to be controlled.
- the height positions of the respective upper surfaces of the p-type semiconductor portion PR and the n-type semiconductor portion NR are substantially the same as the height position of the upper surface of the optical waveguide WO 2 .
- the interlayer insulating film IL 3 is formed such that the interlayer insulating film IL 3 covers the optical waveguides WO 2 , the p-type semiconductor portions PR, and the n-type semiconductor portions NR.
- the optical waveguides WO 2 , the p-type semiconductor portions PR, and the n-type semiconductor portions NR function as a core layer, while the insulating layer CL and the interlayer insulating film IL 3 function as a clad layer.
- the interlayer insulating film IL 3 is made of the multi-layer film including the insulating film IL 1 and the insulating film IL 2 over the insulating film IL 1 . Accordingly, the insulating film IL 1 is in contact with the optical waveguides WO 2 , the p-type semiconductor portions PR, and the n-type semiconductor portions NR.
- respective contact holes (openings) CT are formed to extend through the interlayer insulating film IL 3 (insulating films IL 1 and IL 2 ).
- contact portions (coupling electrodes) CB are formed in the contact holes CT.
- the contact holes CT formed over the p-type semiconductor portions PR are referred to as the contact holes (openings) CT 1
- the contact holes CT formed over the n-type semiconductor portions NR are referred to as the contact holes (openings) CT 2 .
- the contact holes CT 1 formed in the interlayer insulating film IL 3 reach the p-type semiconductor portions PR so that, at the bottom portion of each of the contact holes CT 1 , a portion of the upper surface of the p-type semiconductor portion PR is exposed.
- the contact holes CT 2 formed in the interlayer insulating film IL 3 reach the n-type semiconductor portions NR so that, at the bottom portion of each of the contact hole CT 2 , a portion of the upper surface of the n-type semiconductor portion NR is exposed.
- the contact portions CB formed in the contact holes CT 1 are referred to as the contact portions (coupling electrodes) CB 1
- the contact portions CB formed in the contact holes CT 2 are referred to as the contact portions (coupling electrodes) CB 2
- the contact portions CB 1 formed in the contact holes CT 1 are in contact with the p-type semiconductor portions PR at the bottom portions of the contact holes CT 1 and electrically coupled with the p-type semiconductor portions PR.
- the contact portions CB 2 formed in the contact holes CT 2 are in contact with the n-type semiconductor portions NR at the bottom portions of the contact holes CT 2 and electrically coupled with the n-type semiconductor portions NR. That is, onto the p-type semiconductor portions PR and the n-type semiconductor portions NR, the contact portions CB 1 and CB 2 are coupled respectively as the electrodes (coupling electrodes).
- the optical modulator PC 2 formed in the area AR 3 .
- the optical modulator PC 2 is formed in the area AR 3 .
- the optical modulator PC 2 corresponds to the foregoing optical modulator P 1 in FIG. 1 described above.
- the optical waveguide WO 3 extending in the X-direction is divided at a branch portion into two optical waveguides WO 3 (i.e., an optical waveguide WO 3 a and an optical waveguide WO 3 b ).
- the two optical waveguides WO 3 extend in the X-direction, while being spaced apart from each other in the Y-direction, and are then reunited to form the one optical waveguide WO 3 extending in the X-direction.
- a phase modulation portion PM 2 is provided in each of the two optical waveguides WO 3 a and WO 3 b .
- the phase modulation portion PM 2 is an element which changes the phase of a light beam.
- the phase modulation portion PM 2 provided in the optical waveguide WO 3 a is referred to herein as a phase modulation portion PM 2 a
- the phase modulation portion PM 2 provided in the optical waveguide WO 3 b is referred to herein as a phase modulation portion PM 2 b
- the structure of the phase modulation portion PM 2 a and the structure of the phase modulation portion PM 2 b are basically the same.
- Each of the phase modulation portions PM 2 includes the optical waveguide WO 3 and the heater (heater portion) HT.
- the optical waveguide WO 3 is made of the semiconductor layer SL (silicon layer) and formed over the insulating layer CL.
- the lower surface of the optical waveguide WO 3 is in contact with the upper surface of the insulating layer CL.
- no impurity ion is implanted so that the optical waveguide WO 3 is made of an intrinsic semiconductor (i.e., i-type region).
- the interlayer insulating film IL 3 is formed such that the interlayer insulating film IL 3 covers the optical waveguides WO 3 .
- the optical waveguides WO 3 function as a core layer, while the insulating layer CL and the interlayer insulating film IL 3 function as a clad layer.
- the interlayer insulating film IL 3 is made of the multi-layer film including the insulating film IL 1 and the insulating film IL 2 . Accordingly, the insulating film IL 1 is in contact with the optical waveguides WO 3 .
- the heaters HT are formed over the interlayer insulating film IL 3 (i.e., over the insulating film IL 2 ) and over the optical waveguides WO 3 . Between the optical waveguides WO 3 and the heaters HT, the interlayer insulating film IL 3 (insulating films IL 1 and IL 2 ) is interposed. The heaters HT are disposed over the optical waveguides WO 3 , while the optical waveguides WO 3 and the heaters HT are spaced apart and electrically insulated from each other by the interlayer insulating film IL 3 .
- the heaters HT are elements (heater elements or heating elements) for heating the optical waveguides WO 3 located under the heaters HT.
- the optical waveguide WO 3 a and the heater HT located thereover form the phase modulation portion PM 2 a
- the optical waveguide WO 3 b and the heater HT located thereover form the phase modulation portion PM 2 b .
- Each of the heaters HT is a heat source which changes the temperature of the optical waveguide WO 3 to thus adjust the phase of the optical signal passing through the optical waveguide WO 3 .
- the heater HT when a current is allowed to flow in the heater HT in each of the phase modulation portions PM 2 , the heater HT generates heat.
- the heat generated from the heater HT heats the optical waveguide WO 3 under the heater HT to change (raise) the temperature of the optical waveguide WO 3 . That is, the current allowed to flow in the heater HT allows the temperature of the optical waveguide WO 3 to be controlled.
- the temperature of each of the optical waveguides WO 3 (WO 3 a and WO 3 b ) is changed, the refractive index of the light beam in each of the optical waveguides WO 3 (WO 3 a and WO 3 b ) is changed.
- the wavelength of the light beam traveling in each of the optical waveguides WO 3 is changed to allow the phase of the light beam in the process of traveling in each of the optical waveguides WO 3 (WO 3 a and WO 3 b ) of the phase modulators PM 2 to be changed.
- the incident light beam from an input portion travels in the optical waveguide WO 3 and is divided at the branch portion into two light beams which travel in the two optical waveguides WO 3 a and WO 3 b .
- the two light beams have respective phases controlled in the respective phase modulation portions PM 2 provided in the optical waveguides WO 3 a and WO 3 b and are then reunited into one light beam which travels in the one optical waveguide WO 3 .
- the phase difference between the light beam that has passed through the optical waveguide WO 3 a of the phase modulation portion PM 2 a and the light beam that has passed through the optical waveguide WO 3 b of the phase modulation portion PM 2 b is adjusted to thus allow the phase and intensity of the light beam output from the optical modulator PC 2 to be controlled.
- the germanium optical receiver (photoelectric conversion portion) PD formed in the area AR 4 a description will be given of the germanium optical receiver (photoelectric conversion portion) PD formed in the area AR 4 .
- the germanium optical receiver PD is formed in the area AR 4 .
- the germanium optical receiver PD corresponds to the foregoing optical receiver P 4 .
- the germanium optical receiver PD is a photoelectric conversion element (photoelectric conversion portion or photodetector) which converts an optical signal to an electric signal.
- the germanium optical receiver PD includes the p-type semiconductor portion (semiconductor layer) PRO and the n-type semiconductor portion (semiconductor layer) NRO.
- the p-type semiconductor portion PRO and the n-type semiconductor portion NRO form an element with a pn junction structure (diode with a pn structure) and thus form the germanium optical receiver PD.
- the p-type semiconductor portion PRO is made of the semiconductor layer SL (silicon layer) and formed over the insulating layer CL.
- the lower surface of the p-type semiconductor portion PRO is in contact with the upper surface of the insulating layer CL.
- a p-type impurity is introduced in the p-type semiconductor portion PRO.
- the thickness (height) of the p-type semiconductor portion PRO is about the same as the thickness (height) of each of the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions PR and NR.
- the p-type semiconductor portion PRO is coupled (connected) integrally to the optical waveguide WO 4 .
- the p-type semiconductor portion PRO is coupled (connected) integrally. This allows the optical signal that has propagated in the optical waveguide WO 4 to be introduced into the p-type semiconductor portion PRO.
- the optical waveguide WO 4 is made of the semiconductor layer SL and formed over the insulating layer CL. The lower surface of the optical waveguide WO 4 is in contact with the upper surface of the insulating layer CL. Note that the optical waveguide WO 4 is shown in FIGS. 8 and 9 , but is not shown in the cross section of FIG. 2 .
- the optical waveguide WO 4 In the optical waveguide WO 4 , no impurity ion is implanted so that the optical waveguide WO 4 is made of an intrinsic semiconductor (i type semiconductor). That is, the optical waveguide WO 4 and the p-type semiconductor portion PRO are integrally formed together over the insulating layer CL. However, in the optical waveguide WO 4 , no impurity is introduced, while a p-type impurity is introduced in the p-type semiconductor portion PRO.
- the n-type semiconductor portion NRO is formed over the p-type semiconductor portion PRO.
- the lower surface of the n-type semiconductor portion NRO is in contact with the upper surface of the p-type semiconductor portion PRO.
- a pn junction pn junction surface
- the n-type semiconductor portion NRO is made of a germanium (Ge) layer in which an n-type impurity is introduced.
- the area (two-dimensional size) of the n-type semiconductor portion NRO is smaller than the area (two-dimensional size) of the p-type semiconductor portion PRO.
- the n-type semiconductor portion NRO is included in the p-type semiconductor portion PRO.
- Germanium (Ge) has a forbidden band width smaller than that of silicon (Si). Accordingly, the pn junction formed between n-type germanium and p-type silicon allows a near-infrared light beam at a wavelength not longer than about 1.6 ⁇ m in, e.g., a communication wavelength band to be detected.
- the cap layer CP is formed over the n-type semiconductor portion NRO.
- the cap layer CP is made of silicon (Si) or silicon germanium (SiGe), and more preferably made of silicon (Si).
- the cap layer CP is formed in order to improve surface roughness of germanium contained in the n-type semiconductor portion NRO and ensure the thickness of the layer.
- the two-dimensional shape of the cap layer CP substantially coincides with the two-dimensional shape of the n-type semiconductor portion NRO. It is also possible to regard a combination of the n-type semiconductor portion NRO and the cap layer CP located thereover as a semiconductor portion.
- the germanium optical receiver PD has the p-type semiconductor portion PRO as a first semiconductor portion and a second semiconductor portion over the first semiconductor portion (p-type semiconductor portion PRO).
- the second semiconductor portion has a multi-layer structure including the n-type semiconductor portion NRO and the cap layer CP. That is, more preferably, the second semiconductor portion included in the germanium optical receiver PD includes the germanium layer (semiconductor portion NRO) formed over the first semiconductor portion (p-type semiconductor portion PRO) and further includes the silicon layer (cap layer CP) formed over the germanium layer (semiconductor portion NRO).
- the second semiconductor portion is formed in the opening OP 1 of the insulating film IL 2 .
- the contact hole CT 3 described later reaches the second semiconductor portion.
- the contact portion CB 4 described later is electrically coupled with the second semiconductor portion.
- the interlayer insulating film IL 3 is formed such that the interlayer insulating film IL 3 covers the germanium optical receiver PD (p-type semiconductor portion PRO, n-type semiconductor portion NRO, and cap layer CP).
- the insulating layer CL and the interlayer insulating film IL 3 can function as the clad layer.
- the interlayer insulating film IL 3 is made of the multi-layer film including the insulating film IL 1 and the insulating film IL 2 over the insulating film IL 1 .
- the insulating film IL 1 not the insulating film IL 2 , is in contact with the optical waveguide WO 4 and the p-type semiconductor portion PR.
- the insulating film IL 1 is not formed, but the insulating film IL 2 is formed. This is because, after the multi-layer structure including the n-type semiconductor portion NRO and the cap layer CP is formed in the opening OP 1 formed in the insulating film IL 1 , the insulating film IL 2 is formed. Consequently, the interlayer insulating film IL 3 located over the cap layer CP is made of the insulating film IL 2 , while the interlayer insulating film IL 3 located other than over the cap layer CP is made of the multi-layer film including the insulating film IL 1 and the insulating film IL 2 .
- the respective contact holes CT are formed to extend through the interlayer insulating film IL 3 .
- the contact portions CB are formed.
- the contact hole CT formed over the portion of the p-type semiconductor portion PRO which is uncovered with the n-type semiconductor portion NRO is referred to as the contact hole (opening) CT 3
- the contact hole CT formed over the cap layer CP over the n-type semiconductor portion NRO is referred to as the contact hole (opening) CT 4 .
- the contact holes CT 1 , CT 2 , and CT 3 are formed in the insulating films IL 1 and IL 2 , while the contact hole CT 4 is formed in the insulating film IL 2 .
- the contact hole CT 3 formed in the interlayer insulating film IL 3 reaches the portion of the p-type semiconductor portion PRO which is uncovered with the n-type semiconductor portion NRO. At the bottom portion of the contact hole CT 3 , a portion of the upper surface of the p-type semiconductor portion PRO is exposed.
- the contact hole CT 4 formed in the interlayer insulating film IL 3 reaches the cap layer CP. At the bottom portion of the contact hole CT 4 , a portion of the upper surface of the cap layer CP is exposed.
- the contact portion CB formed in the contact hole CT 3 is referred to as the contact portion (coupling electrode) CB 3
- the contact portion CB formed in the contact hole CT 4 is referred to as the contact portion (coupling electrode) CB 4
- the contact portion CB 3 formed in the contact hole CT 3 is in contact with the p-type semiconductor portion PRO at the bottom portion of the contact hole CT 3 and electrically coupled with the p-type semiconductor portion PRO.
- the contact portion CB 4 formed in the contact hole CT 4 is in contact with the cap layer CP at the bottom portion of the contact hole CT 4 and electrically coupled with the cap layer CP. Note that, in the case where the cap layer CP is not formed, the contact hole CT 4 reaches the semiconductor portion NRO.
- the contact portion CB 4 is in contact with the semiconductor portion NRO at the bottom portion of the contact hole CT 4 and electrically coupled with the semiconductor portion NRO.
- the contact portions CB 3 and CB 4 are coupled respectively as the electrodes (coupling electrodes). This allows a dc current allowed to flow by a photovoltaic effect at the pn junction portion included in the germanium optical receiver PD to be extracted to the outside using the contact portions CB 3 and CB 4 . That is, the optical signal can be extracted as an electric signal.
- the interlayer insulating film IL 4 is formed such that the interlayer insulating film IL 4 covers the heaters HT and the contact portions CB 1 , CB 2 , CB 3 , and CB 4 .
- through holes penetration holes
- conductive plugs PG are embedded.
- the wires M 1 are formed.
- the wires M 1 are the first-layer wires and include the wires M 1 a , M 1 b , M 1 c , M 1 d , and M 1 e.
- the plugs PG are disposed between the wires M 1 a and the contact portions CB 1 and between the wires M 1 b and the contact portions CB 2 .
- the plugs PG are disposed between the wires M 1 c and the heaters HT.
- the plugs PG are disposed between the wire M 1 d and the contact portion CB 3 and between the wire M 1 e and the contact portion CB 4 .
- the plugs PG disposed between the contact portions CB 1 and the wires M 1 a are referred to as the plugs PG 1
- the plugs PG disposed between the contact portions CB 2 and the wires M 1 b are referred to as the plugs PG 2
- the lower surfaces of the plugs PG 1 are in contact with and electrically coupled with the contact portions CB 1
- the upper surfaces of the plugs PG 1 are in contact with and electrically coupled with the wires M 1 a
- the lower surfaces of the plugs PG 2 are in contact with and electrically coupled with the contact portions CB 2
- the upper surfaces of the plugs PG 2 are in contact with and electrically coupled with the wires M 1 b .
- the plugs PG 1 electrically couple the contact portions CB 1 to the wires M 1 a .
- the plugs PG 2 electrically couple the contact portions CB 2 to the wires M 1 b.
- the p-type semiconductor portions PR are electrically coupled with the wires M 1 a via the contact portions CB 1 and the plugs PG 1
- the n-type semiconductor portions NR are electrically coupled with the wires M 1 b via the contact portions CB 2 and the plugs PG 2 .
- This allows voltages to be applied from the wires M 1 a to the p-type semiconductor portions PR via the plugs PG 1 and the contact portions CB 1 and also allows voltages to be applied from the wires M 1 b to the n-type semiconductor portions NR via the plugs PG 2 and the contact portions CB 2 .
- the plugs PG disposed between the heaters HT and the wires M 1 c are referred to as plugs PG 5 .
- the lower surfaces of the plugs PG 5 are in contact with and electrically coupled with the heaters HT, while the upper surfaces of the plugs PG 5 are in contact with and electrically coupled with the wires M 1 c .
- the plugs PG 5 electrically couple the heaters HT to the wires M 1 c . Accordingly, by applying voltages from the wires M 1 c to the heaters HT via the plugs PG 5 , currents are allowed to flow in the heaters HT.
- the temperatures of the optical waveguides WO 3 under the heaters HT are allowed to be controlled. Since the respective plugs PG 5 are coupled to the both end portions of each of the heaters HT, by controlling the difference between the voltage supplied to the plug PG 5 coupled to one of the end portions of the heater HT and the voltage supplied to the plug PG 5 coupled to the other end portion thereof, the current flowing in the heater HT is allowed to be adjusted.
- the plugs PG disposed between the contact portion CB 3 and the wire M 1 d are referred to as the plugs PG 3
- the plugs PG disposed between the contact potion CB 4 and the wire M 1 e are referred to as the plugs PG 4
- the lower surfaces of the plugs PG 3 are in contact with and electrically coupled with the contact portion CB 3
- the upper surfaces of the plugs PG 3 are in contact with and electrically coupled with the wire M 1 d
- the lower surfaces of the plugs PG 4 are in contact with and electrically coupled with the contact portion CB 4
- the upper surfaces of the plugs PG 4 are in contact with and electrically coupled with the wire M 1 e .
- the plugs PG 3 electrically couple the contact portion CB 3 to the wire M 1 d .
- the plugs PG 4 electrically couple the contact portion CB 4 to the wire M 1 e . Consequently, the p-type semiconductor portion PRO is electrically coupled with the wire M 1 d via the contact portion CB 3 and the plugs PG 3 , while the n-type semiconductor portion NRO is electrically coupled with the wire M 1 e via the cap layer CP, the contact portion CB 4 , and the plugs PG 3 .
- an interlayer insulating film IL 5 is formed such that the interlayer insulating film IL 5 covers the wires M 1 .
- through holes penetration holes
- conductive plugs PLG are embedded.
- wires M 2 are formed over the interlayer insulating film IL 5 in which the plugs PLG are embedded.
- the wires M 2 are the second-layer wires.
- the plugs PLG are disposed between the wires M 1 and the wires M 2 to electrically couple the wires M 1 to the wires M 2 .
- a protective film TC is formed such that the protective film TC covers the wires M 2 .
- the interlayer insulating films IL 3 , IL 4 , and IL 5 are made of, e.g., silicon oxide. Silicon oxide is appropriate as the material of the clad layer.
- the protective film TC is made of, e.g., silicon oxynitride. The refractive index n of silicon oxide is about 1.45, while the refractive index n of silicon oxynitride is about 1.82.
- openings OP 2 each exposing a portion of the wire M 2 are formed, and the portions of the wires M 2 which are exposed from the openings OP 2 serve as pad portions (bonding pads or external coupling portions).
- FIGS. 4 and 5 show the case where, in the two optical waveguides WO 2 a and WO 2 b , the respective phase modulation portions PM 1 are provided.
- the phase modulation portion PM 1 is provided in only one of the two optical waveguides WO 2 a and WO 2 b .
- the semiconductor portions NR and PR are provided for, e.g., the optical waveguide WO 2 a , while the semiconductor portions NR and PR are not provided for the optical waveguide WO 2 b.
- FIGS. 6 and 7 show the case where, in the two optical waveguides WO 3 a and WO 3 b , the respective phase modulation portions PM 2 are provided and, for the optical waveguides WO 3 a and WO 3 b , the respective heaters HT are disposed.
- the phase modulation portion PM 2 is provided in only one of the two optical waveguides WO 3 a and WO 3 b .
- the heater HT is provided for, e.g., the optical waveguide WO 3 a , while the heater HT is not provided for the optical waveguide WO 3 b.
- FIGS. 10 to 24 are main-portion cross-sectional views of the semiconductor device in the present first embodiment during the manufacturing process thereof, which show cross sections equivalent to that shown in FIG. 2 described above.
- the SOI substrate SB including the base (supporting substrate) SB 1 , the insulating layer CL formed over the base SB 1 , and the semiconductor layer SL formed over the insulating layer CL is provided.
- the base SB 1 is made of a monocrystalline silicon substrate.
- the insulating layer CL is made of a silicon oxide film and has a thickness of, e.g., about 2 to 3 ⁇ m.
- the semiconductor layer SL is made of a silicon layer (more specifically, a monocrystalline silicon layer) and has a thickness of, e.g., about 180 to 250 nm.
- a method of manufacturing the SOI substrate SB is not limited.
- the SOI substrate SB can be manufactured using, e.g., a SIMOX (Silicon Implanted Oxide) method, a lamination method, a smart cut process, or the like.
- the semiconductor layer SL is patterned using a photolithographic technique and an etching technique to form the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions PR, NR, and PRO.
- a photoresist pattern (not shown) is formed over the semiconductor layer SL using a photolithographic technique. Then, using the photoresist pattern as an etching mask, the semiconductor layer SL is etched to be able to form the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions PR, NR, and PRO. Subsequently, the photoresist pattern is removed by ashing or the like.
- Each of the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions PR, NR, and PRO is made of the patterned semiconductor layer SL and formed over the insulating layer CL.
- the semiconductor portions PR and NR are formed integrally with the optical waveguides WO 2 , while the semiconductor portion PRO is formed integrally with the optical waveguide WO 4 .
- the optical waveguide WO 4 is not shown in the cross sections of FIGS. 11 to 24 , but is shown in FIGS. 8 and 9 described above.
- the optical waveguide WO 4 is formed integrally with the p-type semiconductor portion PRO over the insulating layer CL.
- a p-type impurity is introduced into the semiconductor portion PR using an ion implantation method or the like to change the semiconductor portion PR into the p-type semiconductor portion PR
- an n-type impurity is introduced into the semiconductor portion NR using an ion implantation method or the like to change the semiconductor portion NR into the n-type semiconductor portion NR
- a p-type impurity is introduced into the semiconductor portion PRO using an ion implantation method or the like to change the semiconductor portion PRO into the p-type semiconductor portion PRO.
- the p-type impurity is ion-implanted into the semiconductor portions PR and PRO and, using another photoresist pattern formed using a photolithographic technique as a mask, the n-type impurity is ion-implanted into the semiconductor portion NR.
- the p-type semiconductor portions PR and PRO and the n-type semiconductor portion NR are formed.
- the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 are covered with a photoresist pattern so that the p-type impurity and the n-type impurity are not implanted therein.
- the ion implantation step for introducing the p-type impurity into the semiconductor portion PR may be the same as or different from the ion implantation step for introducing the p-type impurity into the semiconductor portion PRO. After the introduction of the p-type impurity and the n-type impurity, it is also possible to perform heat treatment for activing the introduced impurities.
- the insulating film IL 1 is formed so as to cover the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions NR, PR, and PRO.
- the insulating film IL 1 is preferably made of a silicon oxide film and can be formed using, e.g., a CVD (Chemical Vapor Deposition) method.
- the thickness of the formed insulating film IL 1 is larger than the thickness of the semiconductor layer SL.
- the insulating film IL 1 After the formation of the insulating film IL 1 , it is also possible to perform the polishing of the upper surface of the insulating film IL 1 using a CMP (Chemical Mechanical Polishing) method or the like and planarize the upper surface of the insulating film IL 1 . Even when the upper surface of the insulating film IL 1 is polished, the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions NR, PR, and PRO are not exposed.
- CMP Chemical Mechanical Polishing
- the opening OP 1 is formed in the insulating film IL 1 .
- the two-dimensional size (area) of the opening OP 1 is smaller than the two-dimensional size of the p-type semiconductor portion PRO.
- the opening OP 1 is included in the p-type semiconductor portion PRO.
- the opening OP 1 extends through the insulating film IL 1 to reach the semiconductor portion PRO. At the bottom portion of the opening OP 1 , a portion of the upper surface of the semiconductor portion PRO is exposed.
- the n-type semiconductor portion (germanium layer) NRO made of germanium (Ge) is formed over the p-type semiconductor portion PRO exposed at the bottom portion of the opening OP 1 .
- the n-type semiconductor portion NRO can be formed using an epitaxial growth method and is formed selectively over the p-type semiconductor portion PRO in the opening OP 1 .
- the n-type semiconductor portion NRO can be formed by, e.g., epitaxially growing a germanium (Ge) layer containing an n-type impurity but, in another form, the n-type semiconductor portion NRO can also be formed by epitaxially growing a germanium (Ge) layer as an intrinsic semiconductor and then introducing an n-type impurity into the germanium (Ge) layer by an ion implantation method or the like. In this manner, the element with the pn junction structure including the p-type semiconductor portion PRO made of silicon and the n-type semiconductor portion NRO made of germanium is formed.
- the cap layer CP is selectively formed.
- the cap layer CP is formed so as to improve surface roughness of germanium forming the n-type semiconductor portion NRO or ensure a film thickness.
- the cap layer CP can be formed by, e.g., epitaxially growing a semiconductor layer made of silicon (Si) (semiconductor layer for the cap layer CP) over the n-type semiconductor portion NRO and then introducing an n-type impurity into the semiconductor layer using an ion implantation method.
- the cap layer CP is made of an n-type silicon layer.
- the insulating film IL 2 is formed over the insulating film IL 1 including the cap layer CP.
- the insulating film IL 2 is formed.
- the insulating film IL 2 is preferably made of a silicon oxide film and can be formed using, e.g., a CVD method.
- a combination of the insulating film IL 1 and the insulating film IL 2 corresponds to the interlayer insulating film IL 3 .
- the interlayer insulating film IL 3 is made of the multi-layer film including the insulating film IL 1 and the insulating film IL 2 over the insulating film IL 1 .
- the insulating film IL 2 is formed, but the insulating film IL 1 is not formed.
- the interlayer insulating film IL 3 located over the cap layer CP is made of the insulating film IL 2
- the interlayer insulating film IL 3 except for the portion thereof located over the cap layer CP is made of the multi-layer film including the insulating film IL 1 and the insulating film IL 2 .
- the interlayer insulating film IL 3 is formed over the insulating layer CL so as to cover the optical waveguide WO 1 , the optical waveguide WO 2 , the p-type semiconductor portion PR, the n-type semiconductor portion NR, the optical waveguide WO 3 , the optical waveguide WO 4 , the p-type semiconductor portion PRO, the n-type semiconductor portion NRO, and the cap layer CP.
- the contact holes (openings) CT are formed in the interlayer insulating film IL 3 .
- the contact holes CT include the foregoing contact holes CT 1 , CT 2 , CT 3 , and CT 4 and are formed so as to extend through the interlayer insulating film IL 3 . That is, in the area AR 2 , the contact holes CT 1 are formed over the p-type semiconductor portions PR, while the contact holes CT 2 are formed over the n-type semiconductor portions NR.
- the contact hole CT 3 is formed over the portion of the p-type semiconductor portion PRO which is uncovered with the n-type semiconductor portion NRO, while the contact hole CT 4 is formed over the cap layer CP over the n-type semiconductor portion NRO.
- the contact holes CT 1 are included in the p-type semiconductor portions PR.
- the contact holes CT 1 extend through the interlayer insulating film IL 3 (insulating films IL 2 and IL 1 ) to reach the p-type semiconductor portions PR.
- the contact holes CT 2 are included in the n-type semiconductor portions NR.
- the contact holes CT 2 extend through the interlayer insulating film IL 3 (insulating films IL 2 and IL 1 ) to reach the n-type semiconductor portions NR.
- each of the contact holes CT 2 a portion of the upper surface of the n-type semiconductor portion NR is exposed.
- the contact hole CT 3 is included in the portion of the p-type semiconductor portion PRO which is uncovered with the n-type semiconductor portion NR.
- the contact hole CT 3 extends through the interlayer insulating film IL 3 (insulating films IL 2 and IL 1 ) to reach the p-type semiconductor portion PRO.
- the contact hole CT 4 is included in the cap layer CP over the n-type semiconductor portion NRO.
- the contact hole CT 4 extends through the interlayer insulating film IL 3 (insulating film IL 2 ) to reach the cap layer CP.
- a portion of the upper surface of the cap layer CP is exposed.
- the contact holes CT (CT 1 , CT 2 , CT 3 , and CT 4 ) can be formed as follows. First, over the interlayer insulating film IL 3 , using a photolithographic technique, a photoresist pattern (not shown) is formed. The photoresist pattern has respective openings for the contact holes CT 1 , CT 2 , CT 3 , and CT 4 . Then, using the photoresist pattern as an etching mask, the interlayer insulating film IL 3 is etched to be able to be formed with the contact holes CT 1 , CT 2 , CT 3 , and CT 4 . Subsequently, the photoresist pattern is removed by ashing or the like. In this case, the contact holes CT 1 , CT 2 , CT 3 , and CT 4 are simultaneously formed in the same step.
- the formation of the contact holes CT 1 , CT 2 , and CT 3 and the formation of the contact hole CT 4 can also be performed in different steps. A description will be given also of that case.
- a photoresist pattern (not shown) is formed over the interlayer insulating film IL 3 .
- the photoresist pattern has an opening for the contact hole CT 4 , but does not have respective openings for the contact holes CT 1 , CT 2 , and CT 3 .
- the interlayer insulating film IL 3 is etched to be formed with the contact hole CT 4 .
- the photoresist pattern is removed by ashing or the like, and then another photoresist pattern (not shown) is formed over the interlayer insulating film IL 3 using a photolithographic technique.
- the photoresist pattern formed at this time has respective openings for the contact holes CT 1 , CT 2 , and CT 3 , but does not have an opening for the contact hole CT 4 . Consequently, in the contact hole CT 4 , the photoresist pattern is embedded.
- the interlayer insulating film IL 3 is etched to be formed with the contact holes CT 1 , CT 2 , and CT 3 .
- the photoresist pattern is removed by ashing or the like.
- the contact holes CT 1 , CT 2 , CT 3 , and CT 4 can be formed. In this case, the formation of the contact holes CT 1 , CT 2 , and CT 3 and the formation of the contact hole CT 4 are performed in different steps.
- the contact holes CT 1 , CT 2 , CT 3 , and CT 4 in the same step. This can reduce the number of steps in the manufacturing process of the semiconductor device and reduce the manufacturing cost of the semiconductor device.
- the step of forming the contact hole CT 4 and the step of forming the contact holes CT 1 , CT 2 , and CT 3 are performed separately, the number of steps in the manufacturing process is undesirably increased.
- the advantage of being able of inhibit over-etching of the cap layer CP exposed at the bottom portion of the contact hole CT 4 during the formation of the contact hole CT 4 can be obtained.
- a conductive film (conductor film) CF 1 is formed.
- the conductive film CF 1 is the conductive for forming the heaters HT, but serves also as the conductive film for forming the contact portions CB.
- the conductive film CF 1 is preferably made of a metal material, and more preferably made of a titanium (Ti) film, a titanium nitride (TiN) film, or a multi-layer film including a titanium (Ti) film and a titanium nitride (TiN) film.
- the conductive film CF 1 can be formed using a sputtering method or the like.
- the conductive film CF 1 is formed in the state where the contact holes CT (CT 1 , CT 2 , CT 3 , and CT 4 ) are formed, the conductive film CF 1 is formed not only over the upper surface of the interlayer insulating film IL 3 , but also in the contact holes CT. Specifically, the conductive film CF 1 is formed also over the bottom surfaces and side walls (side surfaces) of the contact holes CT (CT 1 , CT 2 , CT 3 , and CT 4 ).
- the conductive film CF 1 is patterned to form the heaters HT and the contact potions CB (CB 1 , CB 2 , CB 3 , and CB 4 ).
- the heaters HT and the contact portions CB can be formed as follows. First, over the conductive film CF 1 , using a photolithographic technique, a photoresist pattern (not shown) is formed. Then, using the photoresist pattern as an etching mask, the conductive film CF 1 is etched to be able to form the heaters HT and the contact portions CB 1 , CB 2 , CB 3 , and CB 4 . Subsequently, the photoresist pattern is removed by ashing or the like. Each of the heaters HT and the contact portions CB 1 , CB 2 , CB 3 , and CB 4 is made of the patterned conductive film CF 1 .
- the heaters HT, the contact portions CB 1 , the contact portions CB 2 , the contact portion CB 3 , and the contact portion CB 4 are simultaneously formed in the same step, but are unconnected to and detached from each other.
- the heaters HT, the contact portions CB 1 , the contact portions CB 2 , the contact portion CB 3 , and the contact portion CB 4 which are formed by patterning the same conductive film CF 1 , are made of the same material.
- each of the heaters HT and the contact portions CB 1 , CB 2 , CB 3 , and CB 4 is made of a titanium film, a titanium nitride film, or a multi-layer film including a titanium (Ti) film and a titanium nitride (TiN) film.
- the heaters HT are formed over the interlayer insulating film IL 3 and disposed over the optical waveguides WO 3 so as to be able to reliably heat the optical waveguides WO 3 .
- each of the contact portions CB is formed continuously in the contact hole CT and over the interlayer insulating film IL 3 . That is, each of the contact portions CB integrally has a portion made of the conductive film CF 1 in the contact hole CT and a portion made of the conductive film CF 1 over the upper surface of the interlayer insulating film IL 3 . In other words, each of the contact portions CB integrally has the portion located in the contact hole CT and the portion located over the upper surface of the interlayer insulating film IL 3 around the contact hole CT. Accordingly, when the conductive film CF 1 is patterned, the conductive film CF 1 is left in and around the contact holes CT. The conductive film CF 1 remaining in and around the contact holes CT forms the contact portions CB.
- the contact portions CB 1 are formed continuously in the contact holes CT 1 and over the interlayer insulating film IL 3 and integrally has portions located in the contact holes CT 1 and portions located over the upper surface of the interlayer insulating film IL 3 .
- the contact portions CB 1 are in contact with the p-type semiconductor portions PR at the bottom portions of the contact holes CT 1 and electrically coupled with the p-type semiconductor portions PR.
- the contact portions CB 2 are formed continuously in the contact holes CT 2 and over interlayer insulating film IL 3 and integrally has portions located in the contact holes CT 2 and portions located over the upper surface of the interlayer insulating film IL 3 .
- the contact portions CB 2 are in contact with the n-type semiconductor portions NR at the bottom portions of the contact holes CT 2 and electrically coupled with the n-type semiconductor portions NR.
- the contact portion CB 3 is formed continuously in the contact hole CT 3 and over the interlayer insulating film IL 3 and integrally has a portion located in the contact hole CT 3 and a portion located over the upper surface of the interlayer insulating film IL 3 .
- the contact portion CB 3 is in contact with the p-type semiconductor portion PRO at the bottom portion of the contact hole CT 3 and electrically coupled with the p-type semiconductor portion PRO.
- the contact portion CB 4 is formed continuously in the contact hole CT 4 and over the interlayer insulating film IL 3 and integrally has a portion located in the contact hole CT 4 and a portion located over the upper surface of the interlayer insulating film IL 3 .
- the contact portion CB 4 is in contact with the cap layer CP at the bottom portion of the contact hole CT 4 and electrically coupled with the cap layer CP.
- the thickness of the conductive film CF 1 is small and, specifically, smaller than half the diameter of each of the contact holes CT. Consequently, when the conductive film CF 1 is formed, the conductive film CF 1 is formed over the side wall and bottom surface of the contact hole CT, but the contact hole CT is not completely filled with the conductive film CF 1 .
- the formed contact portion CB integrally has a portion extending over the upper surface of the interlayer insulating film IL 3 , a portion extending over the side wall of the contact hole CT, and a portion extending over the bottom surface of the contact hole CT. However, the contact hole CT is not completely filled with the contact portion CB.
- each of the heaters HT is set so as to allow the heater HT to perform the function of a heating element which heats the optical waveguide WO 3 , and the two-dimensional size and thickness of the heater HT are set so as to allow the resistance value to be obtained. Consequently, the thickness of the conductive film CF 1 may be reduced but, in such a case, the contact portions CB shown in FIG. 18 may be formed appropriately.
- the contact hole CT is completely filled with the conductive film CF 1 .
- the formed contact portion CB is integrally provided with a portion extending over the upper surface of the interlayer insulating film IL 3 and a portion filling the contact hole CT so that the contact hole CT is completely filled with the contact portion CB.
- the interlayer insulating film IL 4 is formed so as to cover the heaters HT and the contact portions CB (CB 1 , CB 2 , CB 3 , and CB 4 ).
- the interlayer insulating film IL 4 it is also possible to perform the polishing of the upper surface of the interlayer insulating film IL 4 or the like using a CMP method and thus planarize the upper surface of the interlayer insulating film IL 4 .
- the interlayer insulating film IL 4 is made of a silicon oxide film and can be formed using, e.g., a CVD method.
- through holes (openings) SH are formed in the interlayer insulating film IL 4 .
- the through holes SH are formed so as to extend through the interlayer insulating film IL 4 .
- the through holes SH can be formed as follows. First, using a photolithographic technique, a photoresist pattern is formed over the interlayer insulating film IL 4 . The photoresist pattern has respective openings for the through holes SH. Then, using the photoresist pattern as an etching mask, the interlayer insulating film IL 4 is etched to be able to be formed with the through holes SH. Subsequently, the photoresist pattern is removed by ashing or the like. Through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 are simultaneously formed in the same step.
- the through holes SH include the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 .
- the through holes SH 1 are formed over the contact portions CB 1
- the through holes SH 2 are formed over the contact portions CB 2 .
- the through holes SH 3 are formed over the contact portion CB 3
- the through holes SH 4 are formed over the contact portion CB 4 .
- the through holes SH 5 are formed over the heaters HT.
- the through holes SH 1 are included in the portions of the contact portions CB 1 which are located over the upper surface of the interlayer insulating film IL 3 .
- the through holes SH 1 extend through the interlayer insulating film IL 4 to reach the portions of the contact portion CB 1 which are located over the upper surface of the interlayer insulating film IL 3 .
- the through holes SH 2 are included in the portions of the contact portions CB 2 which are located over the upper surface of the interlayer insulating film IL 3 .
- the through holes SH 2 extend through the interlayer insulating film IL 4 to reach the portions of the contact portions CB 2 which are located over the upper surface of the interlayer insulating film IL 3 . At the bottom portion of each of the through holes SH 2 , a portion of the upper surface of the contact portion CB 2 is exposed. In plan view, the through holes SH 3 are included in the portion of the contact portion CB 3 which is located over the upper surface of the interlayer insulating film IL 3 . The through holes SH 3 extend through the interlayer insulating film IL 4 to reach the portion of the contact portion CB 3 which is located over the upper surface of the interlayer insulating film IL 3 .
- each of the through holes SH 3 a portion of the upper surface of the contact portion CB 3 is exposed.
- the through holes SH 4 are included in the portion of the contact portion CB 4 which is located over the upper surface of the interlayer insulating film IL 3 .
- the through holes SH 4 extend through the interlayer insulating film IL 4 to reach the portion of the contact portion CB 4 which is located over the upper surface of the interlayer insulating film IL 3 .
- the through holes SH 5 are included in the heaters HT located over the upper surface of the interlayer insulating film IL 3 .
- the through holes SH 5 extend through the interlayer insulating film IL 4 to reach the heaters HT located over the upper surface of the interlayer insulating film IL 3 . At the bottom portion of each of the through holes SH 4 , a portion of the upper surface of the heater HT is exposed.
- the respective depths of the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 are substantially the same.
- the conductive plugs PG are formed (embedded).
- the plugs PG can be formed as follows. First, over the interlayer insulating film IL 4 including the bottom surfaces and side walls of the through holes SH, a barrier conductor film is formed. Then, over the barrier conductor film, a main conductor film made of a tungsten film or the like is formed so as to be embedded in the through holes SH.
- the barrier conductor film is made of, e.g., a titanium film, a titanium nitride film, or a multi-layer film thereof. Subsequently, by removing the unneeded main conductor film and the unneeded barrier conductor film which are located outside the through holes SH by a CMP method, an etch-back method, or the like, the plugs PG can be formed. Each of the plugs PG includes the main conductor film and the barrier conductor film which remain in the through hole SH.
- the plugs PG embedded in the through holes SH 1 are the plugs PG 1 .
- the plugs PG 1 are disposed over the portions of the contact portions CB 1 which are located over the upper surface of the interlayer insulating film IL 3 and are in contact with and electrically coupled with the contact portions CB 1 .
- the plugs PG embedded in the through holes SH 2 are the plugs PG 2 .
- the plugs PG 2 are disposed over the portions of the contact portions CB 2 which are located over the upper surface of the interlayer insulating film IL 3 and are in contact with and electrically coupled with the contact portions CB 2 .
- the plugs PG embedded in the through holes SH 3 are the plugs PG 3 .
- the plugs PG 3 are disposed over the portion of the contact portion CB 3 which is located over the upper surface of the interlayer insulating film IL 3 and are in contact with and electrically coupled with the contact portion CB 3 .
- the plugs PG embedded in the through holes SH 4 are the plugs PG 4 .
- the plugs PG 4 are disposed over the portion of the contact portion CB 4 which is located over the upper surface of the interlayer insulating film IL 3 and are in contact with and electrically coupled with the contact portion CB 4 .
- the plugs PG embedded in the through holes SH 5 are the plugs PG 5 .
- the plugs PG 5 are disposed over the heaters HT located over the upper surface of the interlayer insulating film IL 3 and are in contact with and electrically coupled with the heaters HT.
- the respective heights (dimensions in a height direction) of the plugs PG 1 , PG 2 , PG 3 , PG 4 , and PG 5 are substantially the same.
- the wires M 1 are formed.
- the wires M 1 can be formed as follows. First, over the interlayer insulating film IL 4 in which the plugs PG are embedded, a conductive film for forming the wires M 1 is formed.
- the conductive film is made of, e.g., a multi-layer film including a barrier conductor film, a main conductor film located thereover, and a barrier conductor film located thereover.
- the barrier conductor film is made of a titanium film, a titanium nitride film, or a multi-layer film thereof.
- the main conductor film is made of an aluminum film or an aluminum alloy film. Then, over the conductive film, using a photolithographic technique, a photoresist pattern is formed.
- the conductive film is etched to be able to form the wires M 1 .
- the photoresist pattern is removed by ashing or the like.
- Each of the wires M 1 is made of the patterned conductive film.
- the wires M 1 include the foregoing wires M 1 a , M 1 b , M 1 c , M 1 d , and M 1 e .
- the wires M 1 a are electrically coupled with the p-type semiconductor regions PR via the plugs PG 1 and the contact portions CB 1 .
- the wires M 1 b are electrically coupled with the n-type semiconductor regions NR via the plugs PG 2 and the contact portions CB 2 .
- the wires M 1 c are electrically coupled with the heaters HT via the plugs PG 5 .
- the wire M 1 d is electrically coupled with the p-type semiconductor region PRO via the plugs PG 3 and the contact portion CB 3 .
- the wire M 1 e is electrically coupled with the cap layer CP via the plugs PG 4 and the contact portion CB 4 and also electrically coupled with the n-type semiconductor region NR via the cap layer CP.
- the interlayer insulating film IL 5 is formed so as to cover the wires M 1 .
- the interlayer insulating film IL 5 it is also possible to perform the polishing of the upper surface of the interlayer insulating film IL 5 or the like using a CMP method and thus planarize the upper surface of the interlayer insulating film IL 5 .
- the interlayer insulating film IL 5 is preferably made of a silicon oxide film and can be formed using, e.g., a CVD method.
- the plugs PLG can be formed using substantially the same method as used to form the foregoing plugs PG.
- the wires M 2 are formed over the interlayer insulating film IL 5 in which the plugs PLG are embedded.
- the wires M 2 can be formed using substantially the same method as used to form the wires M 1 . That is, a conductive film for forming the wires M 2 is formed over the interlayer insulating film IL 5 in which the plugs PLG are embedded and then patterned using a photolithographic technique and an etching technique to be able to form the wires M 2 .
- the plugs PLG are disposed between the wires M 2 and the wires M 1 to electrically couple the wires M 2 to the wires M 1 .
- the protective film TC is formed so as to cover the wires M 2 .
- the protective film TC is made of, e.g., a silicon oxynitride film and can be formed using a CVD method or the like.
- the openings OP 2 are formed in the protective film TC. From each of the openings OP 2 of the protective film TC, a portion of the wire M 2 is exposed. The portions of the wires M 2 which are exposed from the openings OP 2 serve as the pad portions (bonding pads or external coupling portions). Subsequently, the SOI substrate SB is diced (cut) together with the structure located thereover to be singulated. In this manner, semiconductor chips (semiconductor devices) are obtained.
- the semiconductor device in the present first embodiment can be manufactured.
- FIG. 25 is a main-portion cross-sectional view of the semiconductor device in the studied example studied by the present inventors and shows a cross-sectional view of a region equivalent to that shown in FIG. 2 described above. Note that, in FIG. 25 , for simpler illustration, the depiction of the foregoing interlayer insulating film IL 5 and the structure located thereover is omitted.
- the semiconductor device in the studied example shown in FIG. 25 includes the base SB 1 , the insulating layer CL formed over the base SB 1 , the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions PR, NR, and PRO which are formed over the insulating layer CL, the semiconductor portion NRO formed over the semiconductor portion PRO, and the cap layer CP formed over the semiconductor portion NRO, similarly to the semiconductor device in the present first embodiment.
- the optical waveguide WO 4 is shown in FIGS. 8 and 9 described above, but is not shown in FIGS. 2 and 25 described above.
- each of the heaters HT is formed over the interlayer insulating film IL 3 and over the corresponding optical waveguide WO 3 .
- wires M 101 a , M 101 b , M 101 c , M 101 d , and M 101 e are formed over the interlayer insulating film IL 4 .
- the semiconductor device in the studied example is different from that in the present first embodiment in the manner in which the wires M 101 a , M 101 b , M 101 c , M 101 d , and M 101 e are coupled to the semiconductor portions PR, NR, PRO, and NRO and the heater HT.
- the wires M 101 a , M 101 b , M 101 c , M 101 d , and M 101 e are coupled directly to the semiconductor portions PR, NR, and PRO, the cap layer CP, and the heater HT via conductive plugs PG 101 , PG 102 , PG 103 , PG 104 , and PG 105 .
- the wire M 101 a is electrically coupled with the p-type semiconductor portion PR via the plug PG 101 embedded in a contact hole CT 101 extending through the interlayer insulating films IL 3 and IL 4 .
- the wire M 101 b is electrically coupled with the n-type semiconductor portion NR via the plug PG 102 embedded in a contact hole CT 102 extending through the interlayer insulating films IL 3 and IL 4 .
- the wire M 101 c is electrically coupled with the heater HT via the plug PG 105 embedded in a contact hole CT 105 extending through the interlayer insulating film IL 4 .
- the wire M 101 d is electrically coupled with the p-type semiconductor portion PRO via the plug PG 103 embedded in a contact hole CT 103 extending through the interlayer insulating films IL 3 and IL 4 .
- the wire M 101 e is electrically coupled with the cap layer CP via the plug PG 104 embedded in a contact hole CT 104 extending through the interlayer insulating films IL 3 and IL 4 and also to the n-type semiconductor portion NRO via the cap layer CP.
- FIGS. 26 to 30 are main-portion cross-sectional views of the semiconductor device in the studied example during the manufacturing process thereof and show cross sections equivalent to that shown in FIG. 25 described above.
- the manufacturing process of the semiconductor device in the studied example and the manufacturing process of the semiconductor device in the present first embodiment described above are substantially the same until the structure in FIG. 15 described above is obtained by forming the insulating film IL 2 over the insulating film IL 1 including the cap layer CP and polishing the upper surface of the insulating film IL 2 by a CMP method.
- the step of forming the foregoing contact holes CT is not performed, but a conductive film CF 101 is formed over the interlayer insulating film IL 3 as shown in FIG. 26 . Then, as shown in FIG. 27 , the conductive film C 101 is patterned to form the heaters HT. However, in the case of the studied example, no equivalent to the foregoing contact portions CB 1 , CB 2 , CB 3 , and CB 4 is formed.
- the interlayer insulating film IL 4 is formed so as to cover the heaters HT.
- the polishing of the upper surface of the interlayer insulating film IL 4 or the like is performed using a CMP method to planarize the upper surface of the interlayer insulating film IL 4 .
- the contact holes CT 101 , CT 102 , CT 103 , CT 104 , and CT 105 are formed in the interlayer insulating films IL 4 and IL 3 .
- the contact hole CT 101 extends through the interlayer insulating film IL 4 , the insulating film IL 2 , and the insulating film IL 1 . At the bottom portion of the contact hole CT 101 , a portion of the p-type semiconductor portion PR is exposed.
- the contact hole CT 102 extends through the interlayer insulating film IL 4 , the insulating film IL 2 , and the insulating film IL 1 . At the bottom portion of the contact hole CT 102 , a portion of the n-type semiconductor portion NR is exposed.
- the contact hole CT 103 extends through the interlayer insulating film IL 4 , the insulating film IL 2 , and the insulating film IL 1 .
- the contact hole CT 104 extends through the interlayer insulating film IL 4 and the insulating film IL 2 .
- a portion of the cap layer CP is exposed.
- the contact hole CT 105 extends through the interlayer insulating film IL 4 .
- a portion of the heater HT is exposed.
- the conductive plugs PG 101 , PG 102 , PG 103 , PG 104 , and PG 105 are formed.
- the wires M 101 a , M 101 b , M 101 c , M 101 d , and M 101 e are formed.
- the foregoing interlayer insulating film IL 5 is formed so as to cover the wires M 101 a to M 101 e , but the illustration and description thereof is omitted herein.
- the present inventors have considered introducing an optical modulator which uses heating involving the use of a heater in a semiconductor device to which a silicon photonics technique is applied. Accordingly, as described above, the present inventors have considered forming the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 , the semiconductor portions PR, NR, PRO, and NRO, and the heaters TH in the same semiconductor device (semiconductor chip).
- the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions PR, NR, and PRO are made of the same material (silicon) and can be formed by patterning the SOI layer (foregoing semiconductor layer SL) of the SOI substrate. Accordingly, each of the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions PR, NR, and PRO is formed over the insulating layer CL, i.e., formed in the same layer.
- the semiconductor portion NRO provided so as to form a photoelectric conversion element is made of a material (specifically, germanium) different from that of each of the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions PR, NR, and PRO. Consequently, the semiconductor portion NRO cannot be formed by patterning the semiconductor layer SL and therefore needs to be formed in a layer different from the layer in which the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions PR, NR, and PRO are formed. Accordingly, the semiconductor portion NRO is formed over the semiconductor portion PRO.
- the heaters HT are made of a material different from that of each of the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions PR, NR, and PRO, and is also made of a material different from that of the semiconductor portion NRO.
- the resistance of each of the heaters is also reduced. Consequently, it is difficult to ensure the function of the heater, and therefore it is desirable to separately form the heaters HT in a layer different from the layer in which the wires M 1 are formed.
- the heaters HT in a layer different from the layer in which the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions PR, NR, and PRO are formed, also different from the layer in which the semiconductor portion NRO is formed, and also different from the layer in which the wires M 1 are formed.
- the layer in which the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions PR, NR, and PRO are formed, the layer in which a multi-layer structure including the semiconductor portion NRO and the cap layer CP is formed, and the layer in which the heaters HT are formed are at different height positions, and the layer in which the heaters HT are formed is at a highest position.
- the optical waveguides WO 2 , WO 3 , and WO 4 and the semiconductor portions PR, NR, and PRO are formed.
- the multi-layer structure including the semiconductor portion NRO and the cap layer CP is formed.
- the heaters HT are formed over the interlayer insulating film IL 3 .
- the heaters HT and the semiconductor portions PR, NR, PRO, and NRO need to be electrically coupled with the wires provided over the interlayer insulating film IL 4 .
- the plug PG 101 is embedded in the contact hole CT 101 extending through the interlayer insulating film IL 4 and the insulating films IL 2 and IL 1 and, through the plug PG 101 , the p-type semiconductor portion PR is electrically coupled with the wire M 101 a over the interlayer insulating film IL 4 .
- the plug PG 102 is embedded in the contact hole CT 102 extending through the interlayer insulating film IL 4 and the insulating films IL 2 and IL 1 and, through the plug PG 102 , the n-type semiconductor portion NR is electrically coupled with the wire M 101 b over the interlayer insulating film IL 4 .
- the plug PG 103 is embedded in the contact hole CT 103 extending through the interlayer insulating film IL 4 and the insulating films IL 2 and IL 1 and, through the plug PG 103 , the p-type semiconductor portion PRO is electrically coupled with the wire M 101 d over the interlayer insulating film IL 4 .
- the plug PG 104 is embedded in the contact hole CT 104 extending through the interlayer insulating film IL 4 and the insulating film IL 2 and, through the plug PG 104 , the cap layer CP is electrically coupled with the wire M 101 e over the interlayer insulating film IL 4 .
- the plug PG 105 is embedded in the contact hole CT 105 extending through the interlayer insulating film IL 4 and, through the plug PG 105 , the heater HT is electrically coupled with the wire M 101 c over the interlayer insulating film IL 4 .
- the depth of the contact hole CT 104 is larger than the depth of the contact hole CT 105 , and the respective depths of the contact holes CT 101 , CT 102 , and CT 103 are larger than the depth of the contact hole CT 104 . That is, the depth of the contact hole CT 105 is rather small, while the depth of the contact hole CT 104 is considerably large, and the respective depths of the contact holes CT 101 , CT 102 , and CT 103 are larger than the depth of the contact hole CT 104 .
- the distances between the heater HT and the optical waveguides WO 3 need to be set rather large, the differences between the depth of the contact hole CT 105 and the depths of the other contact holes CT 101 , CT 102 , CT 103 , and CT 104 are set large.
- an amount of over-etching of the cap layer CP exposed at the bottom portion of the contact hole CT 104 is larger than an amount of over-etching of each of the semiconductor portions PR, NR, and PRO exposed at the bottom portions of the contact holes CT 101 to CT 103
- an amount of over-etching of the heater HT exposed at the bottom portion of the contact hole CT 105 is larger than the amount of the over-etching of the cap layer CP exposed at the bottom portion of the contact hole CT 104 .
- the amount of over-etching needs to be set such that the deepest contact holes CT 101 and CT 103 are surely opened. Since it is common to set the amount of over-etching at a predetermined ratio relative to the depth of a contact hole to be formed, when the depth of the contact hole intended to be formed is increased, the set amount of over-etching also needs to be increased. Showing an example, a description will be given thereof.
- etching is performed by setting the amount of over-etching to 200 nm corresponding to 40% of the depth of the contact hole and assuming that an amount of etching which allows the silicon oxide film to be etched by 700 nm is the total amount of etching.
- etching is performed by setting the amount of over-etching to 400 nm corresponding to 40% of the depth of the contact hole and assuming that an amount of etching which allows the silicon oxide film to be etched by 1400 nm is the total amount of etching. This allows the contact hole to be surely opened even when conditions in the manufacturing device unintentionally fluctuate. As a result, the amount of over-etching is larger in the case where the contact hole having a depth of 1000 nm is formed in the silicon oxide film than in the case where the contact hole having a depth of 500 nm is formed in the silicon oxide film.
- the amount of over-etching during the formation of the contact holes CT 101 to CT 105 needs to be set considerably large on the basis of the deeper contact holes CT 101 to CT 103 .
- Each of the heaters HT is disposed over the corresponding optical waveguide WO 3 so as to heat the optical waveguide WO 3 , and the distance between the heater HT and the optical waveguide WO 3 needs to be set rather large.
- This functions to increase the depths of the contact holes CT 101 to CT 103 and also increase the differences between the depths of the contact holes CT 101 to CT 103 and the contact hole CT 105 and consequently functions to increase over-etching of each of the semiconductor portions PR, NR, and PRO, the cap layer CP, and the heaters HT.
- the semiconductor portion NR needs to have a rather large thickness.
- increasing the thickness of the semiconductor portion NR functions to increase the depths of the contact holes CT 101 to CT 103 and also increase the differences between the depths of the contact holes CT 101 to CT 103 and the contact hole CT 104 and therefore functions to increase over-etching of the cap layer CP.
- the thickness of the cap layer CP cannot be excessively increased. Consequently, when the amount of over-etching of the cap layer CP is increased, the cap layer CP disappears as a result of being over-etched and even the semiconductor portion NRO may be over-etched.
- the amount of over-etching of each of the semiconductor portions PR, NR, and PRO exposed at the bottom portions of the contact holes CT 101 to CT 103 is considerably increased, the amount of over-etching of the cap layer CP exposed at the bottom portion of the contact hole CT 104 is further increased, and the amount of over-etching of the heater HT exposed at the bottom portion of the contact hole CT 105 is further increased.
- the increased amount of over-etching of each of the semiconductor portions PR, NR, and PRO, the cap layer CP, and the heater HT which are exposed at the bottom portions of the contact holes CT 101 to CT 105 may degrade the reliability of the manufactured semiconductor device.
- each of the contact holes CT 101 to CT 103 leads to an increase in the aspect ratio (length-width ratio) of each of the contact holes CT 101 to CT 103 .
- This increases the difficulty with which the contact holes CT 101 to CT 103 are opened by etching and may cause defective formation of the contact holes CT 101 to CT 103 .
- the reliability of the manufactured semiconductor device may be degraded.
- One of the main characteristic features of the present first embodiment is that, over the semiconductor portions PR, NR, PRO, and NRO, the contact portions CB 1 , CB 2 , CB 3 , and CB 4 electrically coupled individually thereto are provided.
- the wires M 1 a , M 1 b , M 1 c , M 1 d , and M 1 e formed over the interlayer insulating film IL 4 are electrically coupled with the heaters HT and the contact portions CB 1 , CB 2 , CB 3 , and CB 4 via the plugs PG 1 , PG 2 , PG 3 , PG 4 , and PG 5 embedded in the interlayer insulating film IL 4 .
- the wires M 1 c formed over the interlayer insulating film IL 4 are electrically coupled with the heaters HT via the plugs PG 5 , while the wires M 1 a , M 1 b , M 1 d , and M 1 e formed over the interlayer insulating film IL 4 are electrically coupled with the semiconductor portions PR, NR, and PRO and the cap layer CP via the plugs PG (PG 1 , PG 2 , PG 3 , and PG 4 ) and the contact portions CB (CB 1 , CB 2 , CB 3 , and CB 4 ).
- the heaters HT are formed over the interlayer insulating film IL 3 , while each of the contact portions CB (CB 1 , CB 2 , CB 3 , and CB 4 ) is formed continuously in the contact hole CT (CT 1 , CT 2 , CT 3 , or CT 4 ) provided in the interlayer insulating film IL 3 and over the interlayer insulating film IL 3 .
- the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 provided for the formation of the plugs PG 1 , PG 2 , PG 3 , PG 4 , and PG 5 may be formed appropriately in the interlayer insulating film IL 4 .
- the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 have substantially the same depths, which are considerably small.
- the respective depths of the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 are considerably smaller than the respective depths of the foregoing contact holes CT 101 , CT 102 , and CT 103 in the foregoing comparative example and about the same as the depth of the foregoing contact hole CT 105 .
- the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 are formed in the interlayer insulating film IL 4 , the amount of over-etching of each of the contact portions CB 1 , CB 2 , CB 3 , and CB 4 and the heaters HT which are exposed at the bottom portions of the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 can considerably be reduced. As a result, during the formation of the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 in the interlayer insulating film IL 4 , a problem resulting from over-etching is less likely to occur.
- the semiconductor portions PR, NR, PRO, and NRO and the cap layer CP are not exposed. Consequently, when the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 are formed in the interlayer insulating film IL 4 , there is no concern about over-etching of the semiconductor portions PR, NR, PRO, and NRO and the cap layer CP.
- the contact holes CT 1 , CT 2 , CT 3 , and CT 4 it is necessary to form the contact holes CT 1 , CT 2 , CT 3 , and CT 4 in the interlayer insulating film IL 3 .
- the interlayer insulating film IL 4 need not be etched, and it is sufficient to etch the interlayer insulating film IL 3 .
- the respective depths of the contact holes CT 1 , CT 2 , CT 3 , and CT 4 are not so large. Specifically, the depths of the contact holes CT 1 , CT 2 , CT 3 , and CT 4 are considerably smaller than the depths of the foregoing contact holes CT 101 , CT 102 , and CT 103 in the foregoing comparative example.
- the depths of the contact holes CT 1 , CT 2 , and CT 3 are substantially the same, while the depth of the contact hole CT 4 is smaller than those of the contact holes CT 1 , CT 2 , and CT 3 .
- the contact holes CT 1 , CT 2 , CT 3 , and CT 4 having unequal depths are formed by the same etching step, it is necessary to perform the etching on the basis of the depths of the deepest contact holes CT 1 , CT 2 , and CT 3 .
- the amount of over-etching in the etching step for forming the contact holes CT 1 , CT 2 , CT 3 , and CT 4 needs to be set larger.
- the present first embodiment it is possible to reduce the amount of over-etching of each of the semiconductor portions PR, NR, and PRO exposed at the bottom portions of the contact holes CT 1 , CT 2 , and CT 3 and reduce the amount of over-etching of the cap layer CP exposed at the bottom portion of the contact hole CT 4 .
- This can inhibit or prevent the occurrence of a problem resulting from over-etching during the formation of the contact holes CT 1 , CT 2 , CT 3 , and CT 4 in the interlayer insulating film IL 3 and improve the reliability of the manufactured semiconductor device.
- the present first embodiment it is possible to inhibit or prevent the occurrence of a problem resulting from over-etching during the formation of the contact holes CT 1 , CT 2 , CT 3 , and CT 4 in the interlayer insulating film IL 3 and during the formation of the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 in the interlayer insulating film IL 4 .
- This can improve the reliability of the manufactured semiconductor device.
- the respective depths of the contact holes CT 1 , CT 2 , CT 3 , and CT 4 and the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 can be reduced, the respective aspect ratios thereof can be reduced.
- the contact holes CT 1 , CT 2 , CT 3 , and CT 4 and the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 are more easily opened by etching, and defective formation of the contact holes CT 1 , CT 2 , CT 3 , and CT 4 and the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 can be prevented.
- the reliability of the manufactured semiconductor device can be improved.
- Techniques for inhibiting over-etching include a technique using an etching stopper film.
- a contact hole is formed in a multi-layer film including a silicon nitride film and a silicon oxide film.
- the silicon oxide film is etched, the silicon nitride film is caused to function as an etching stopper and then, under changed etching conditions, the silicon nitride film is etched to thus complete the contact hole.
- the interlayer insulating film IL 3 functions as the clad layer. Accordingly, the insulating layer CL and the interlayer insulating film IL 3 are preferably formed of the same material, and more preferably formed of silicon oxide.
- the insulating layer CL and the interlayer insulating film IL 3 can be formed of the same material and, more preferably, can be formed of silicon oxide. This can enhance the function of the insulating layer CL and the interlayer insulating film IL 3 as the clad layer.
- the heaters HT and the contact portions CB 1 , CB 2 , CB 3 , and CB 4 are formed by patterning the same conductive film CF 1 . That is, by additionally performing the step of forming the contact holes CT 1 , CT 2 , CT 3 , and CT 4 after the formation of the insulating film IL 2 and before the formation of the conductive film CF 1 , the contact portions CB 1 , CB 2 , CB 3 , and CB 4 can also be formed simultaneously with the heaters HT. This can reduce the number of steps in the manufacturing process of the semiconductor device even when the contact portions CB 1 , CB 2 , CB 3 , and CB 4 are formed and thus reduce the manufacturing cost of the semiconductor device.
- the contact portions CB 1 , CB 2 , CB 3 , and CB 4 are formed by patterning the same conductive film CF 1 , the contact portions CB 1 , CB 2 , CB 3 , and CB 4 have respective portions located (extending) over the interlayer insulating film IL 3 .
- the plugs PG 1 , PG 2 , PG 3 , and PG 4 can be coupled easily and reliably to the contact portions CB 1 , CB 2 , CB 3 , and CB 4 .
- the heaters HT and the contact portions CB 1 , CB 2 , CB 3 , and CB 4 are formed in different layers, it indicates that the heaters HT and the contact portions CB 1 , CB 2 , CB 3 , and CB 4 are not formed by patterning the same conductive film. In such a case, a large number of steps are needed to form the heaters HT and the contact portions CB 1 , CB 2 , CB 3 , and CB 4 .
- the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 are not allowed to have equal depths to raise a concern about over-etching during the formation of the through holes SH 1 , SH 2 , SH 3 , SH 4 , and SH 5 . In the present first embodiment, such a situation can be avoided.
- the semiconductor portion NRO under the cap layer CP which is made of germanium (Ge), has low resistance to heat.
- the plug PG 104 is formed in the state where the cap layer CP is exposed from the contact hole CT 104 .
- each of the plugs PG 101 to PG 105 includes a tungsten (W) film as a main conductor film and, during the deposition of the tungsten film, the semiconductor portion NRO made of germanium (Ge) may be heated and degraded.
- each of the plugs PG 1 to PG 5 includes a tungsten (W) film as a main conductor film, but is considerably distant from the cap layer CP and the semiconductor portion NRO.
- the conductive film CF 1 is formed in the state where the cap layer CP is exposed from the contact hole CT 4 but, as described above, the conductive film CF 1 is made of a titanium film, a titanium nitride film, or a multi-layer film thereof. While being deposited, a titanium film and a titanium nitride film are more likely to inhibit the underlay from being heated than a tungsten film.
- the present first embodiment can improve the reliability of the manufactured semiconductor device.
- the contact holes CT 1 , CT 2 , CT 3 , and CT 4 can be formed by the same step.
- the step of forming the contact hole CT 4 and the step of forming the contact holes CT 1 , CT 2 , and CT 3 are separately performed, the advantage of being able to further inhibit over-etching of the cap layer CP exposed at the bottom portion of the contact hole CT 4 can be obtained.
- the depths of the contact holes CT 1 , CT 2 , CT 3 , and CT 4 are relatively small. Accordingly, the photoresist pattern embedded in the contact holes CT 1 , CT 2 , and CT 3 or in the contact hole CT 4 can be removed easily and reliably by ashing. As a result, in the present first embodiment, even when the formation of the contact holes CT 1 , CT 2 , and CT 3 and the formation of the contact hole CT 4 are performed in different steps, it is possible to prevent the unremoved residues of the photoresist pattern from being left.
- the conductive film CF 101 is patterned using the photoresist pattern formed over the conductive film CF 101 as an etching mask to form the heaters HT.
- alignment marks e.g., stepped portions or recessed portions in the conductive film CF 101 . This causes the need for the step of processing the interlayer insulating film IL 3 before the step of forming the conductive film CF 101 so as to allow the alignment marks to be formed in the conductive film CF 101 .
- the conductive film CF 1 is formed and then patterned using the photoresist pattern formed over the conductive film CF 1 as an etching mask to form the heaters HT and the contact portions CB 1 , CB 2 , CB 3 , and CB 4 .
- the exposure step when the photoresist pattern is formed stepped portions or recessed portions resulting from the contact holes CT are formed in the conductive film CF 1 , and therefore can be used as alignment marks. Accordingly, after the formation of the contact holes CT and before the step of forming the conductive film CF 1 , it is unnecessary to perform a processing step for forming alignment marks on the interlayer insulating film IL 3 .
- the semiconductor device in the present first embodiment has both of the optical modulator PC 1 having a configuration in which voltages are applied to the semiconductor portions PR and NR and the optical modulator PC 2 having a configuration in which the optical waveguides WO 3 are heated using the heaters HT.
- the semiconductor device at least the one or more optical modulators PC 1 and at least the one or more optical modulator PC 2 are embedded.
- the semiconductor device has the optical modulator PC 2 having the configuration in which the optical waveguides WO 3 are heated using the heaters HT, but does not have the optical modulator PC 1 having the configuration in which voltages are applied to the semiconductor portions PR and NR.
- the one or more optical modulators PC 2 each having the configuration in which the optical waveguides WO 3 are heated using the heaters HT are embedded in the semiconductor device.
- the formation of the foregoing optical waveguides WO 2 , the p-type semiconductor portions PR, the n-type semiconductor portions NR, the contact portions CB 1 and CB 2 , the plugs PG 1 and PG 2 , and the wires M 1 a and M 1 b is omitted.
- FIG. 31 is a main-portion cross-sectional view of the semiconductor device in the present second embodiment.
- FIGS. 33 and 34 are main-portion plan views of the semiconductor device in the present second embodiment.
- FIG. 31 shows a cross-sectional view of the area AR 3 .
- FIGS. 32 and 33 show plan views of the area AR 3 . A cross-sectional view at a position along the line A 5 -A 5 in FIG. 32 corresponds to FIG. 31 . Note that FIGS. 32 and 33 show the plan views of the same area but, in FIG.
- the optical waveguides WO 3 and semiconductor portions SM 1 and SM 2 are shown by the solid lines
- contact holes CT 5 and CT 6 are shown by two-dot-dash lines
- the heaters HT are shown by the broken lines.
- the optical waveguides WO 3 , the heaters HT, and the plugs PG 5 are shown by the solid lines
- the wires M 1 c are shown by the two-dot-dash lines.
- the optical waveguide WO 3 extending in the X-direction in the area AR 3 is divided at a branch portion into the two optical waveguides WO 3 (i.e., WO 3 a and WO 3 b ).
- the two optical waveguides WO 3 extend in the X-direction, and are then reunited to form the one optical waveguide WO 3 extending in the X-direction.
- the phase modulation portion PM 2 is provided in each of the two optical waveguides WO 3 a and WO 3 b .
- the structure of the phase modulation portion PM 2 in the present second embodiment is different from that in the foregoing first embodiment.
- phase modulation portion PM 2 i.e., the phase modulation portion PM 2 a
- the configuration of the phase modulation portion PM 2 i.e., the phase modulation portion PM 2 b
- the phase modulation portion PM 2 is not provided in one of the optical waveguides WO 3 a and WO 3 b.
- each of the phase modulation portions PM 2 includes the optical waveguide WO 3 , the semiconductor portions SM 1 and SM 2 , and the heater (heater portion) HT.
- Each of the optical waveguide WO 3 and the semiconductor portions SM 1 and SM 2 is made of the semiconductor layer SL and formed over the insulating layer CL.
- the configuration of the optical waveguide WO 3 is the same as in the foregoing first embodiment.
- the semiconductor portion SM 1 and the semiconductor portion SM 2 may be i-type regions in which no impurity ion is implanted, n-type regions in which n-type impurity ions are implanted, or p-type regions where p-type impurity ions are implanted.
- the semiconductor portions SM 1 and SM 2 are located opposite to each other relative to the optical waveguide WO 3 being interposed therebetween. That is, between the semiconductor portion SM 1 and the semiconductor portion SM 2 which are spaced apart from each other in the Y-direction, the optical waveguide WO 3 extending in the X-direction is disposed.
- the optical waveguide WO 3 , the semiconductor portion SM 1 , and the semiconductor portion SM 2 are spaced apart from and unconnected to each other. Each of the semiconductor portion SM 1 and the semiconductor portion SM 2 is a detached pattern. Accordingly, to the semiconductor portions SM 1 and SM 2 , no optical waveguide is connected so that no optical signal is transmitted thereto.
- the interlayer insulating film IL 3 (insulating films IL 1 and IL 2 ) is formed so as to cover the optical waveguides WO 3 and the semiconductor portions SM 1 and SM 2 .
- the respective contact holes CT extending through the interlayer insulating film IL 3 are formed. Note that the contact holes CT formed over the semiconductor portions SM 1 are referred to as the contact holes (openings) CT 5 , while the contact holes CT formed over the semiconductor portions SM 2 are referred to as the contact holes (openings) CT 6 .
- the contact holes CT 5 reach the semiconductor portions SM 1 and, at the bottom portion of each of the contact holes CT 5 , a portion of the upper surface of the semiconductor portion SM 1 is exposed.
- the contact holes CT 6 reach the semiconductor portions SM 2 and, at the bottom portion of each of the contact holes CT 6 , a portion of the upper surface of the semiconductor portion SM 2 is exposed.
- each of the heaters HT integrally has a heater main body portion (first portion) HTa formed over the interlayer insulating film IL 3 and over the optical waveguide WO 3 , a contact portion (second portion) CB 5 formed in the contact hole CT 5 , and a contact portion (third portion) CB 6 formed in the contact hole CT 6 .
- the heaters HT are elements for heating the optical waveguides WO 3 .
- the heaters HT are spaced apart and electrically insulated from the optical waveguides WO 3 .
- the heater main body portion HTa is equivalent to the heater HT in the foregoing first embodiment.
- a combination of the heater HT in the foregoing first embodiment HT and the contact portions CB 5 and CB 6 connected integrally thereto corresponds to the heater HT in the present second embodiment.
- the heater main body portion HTa is disposed over the optical waveguide WO 3 .
- the structures of the contact portions CB 5 and CB 6 are similar to those of the contact portions CB 1 , CB 2 , and CB 3 .
- the contact portions CB 1 , CB 2 , and CB 3 are members (patterns) independent of each other, while the contact portions CB 5 and CB 6 are connected integrally to the heater main body portion HTa.
- each of the contact portions CB 5 integrally has a portion extending over the upper surface of the interlayer insulating film IL 3 , a portion extending over the side wall of the contact hole CT 5 , and a portion extending over the bottom surface of the contact hole CT 5 .
- each of the contact portions CB 6 integrally has a portion extending over the upper surface of the interlayer insulating film IL 3 , a portion extending over the side wall of the contact hole CT 6 , and a portion extending over the bottom surface of the contact hole CT 6 .
- each of the heaters HT in the present second embodiment integrally has a portion extending over the upper surface of the interlayer insulating film IL 3 , a portion extending over the side wall of the contact hole CT 5 , a portion extending over the bottom surface of the contact hole CT 5 , a portion extending over the side wall of the contact hole CT 6 , and a portion extending over the bottom surface of the contact hole CT 6 .
- the interlayer insulating film IL 4 is formed so as to cover the heaters HT, the through holes SH 5 are formed in the interlayer insulating film IL 4 , and the conductive plugs PG 5 are embedded in the through holes SH 5 .
- the wires M 1 c are formed.
- the plugs PG 5 are disposed between the wires M 1 c and the heaters HT (heater main body portions HTa) to electrically couple the wires M 1 c with the heaters HT.
- the semiconductor layer SL is patterned to form not only the optical waveguides WO 1 , WO 2 , WO 3 , and WO 4 and the semiconductor portions NR, PR, and PRO, but also the semiconductor portions SM 1 and SM 2 .
- the step of forming the contact holes CT not only the contact holes CT 1 , CT 2 , CT 3 , and CT 4 , but also the contact holes CT 5 and CT 6 (see FIG. 31 ) are formed.
- the semiconductor portions SM 1 and SM 2 are not formed unlike in the present second embodiment, not only the contact holes CT 5 and CT 6 extend through the interlayer insulating film IL 3 , but also the etching of the insulating layer CL undesirably proceeds at the bottom portions of the contact holes CT 5 and CT 6 .
- the semiconductor portions SM 1 and SM 2 are provided and, over the semiconductor portions SM 1 and SM 2 , the contact holes CT 5 and CT 6 are disposed. This can stop the etching for the contact holes CT 5 and CT 6 at the semiconductor portions SM 1 and SM 2 .
- the semiconductor portions SM 1 and SM 2 are not provided as regions to which voltages are to be applied or as transmission paths for light beams, but are provided so as to allow the contact holes CT 5 and CT 6 and the contact potions CB 5 and CB 6 to be reliably formed.
- the contact portions CB 5 are electrically coupled with the semiconductor portions SM 1 and the contact portions CB 6 are electrically coupled with the semiconductor portions SM 2 , but the electric coupling is not an essential requirement.
- the conductive film CF 1 is formed not only over the upper surface of the interlayer insulating film IL 3 (i.e., the upper surface of the insulating film IL 2 ), but also in the contact holes CT 1 , CT 2 , CT 3 , CT 4 , CT 5 , and CT 6 .
- the conductive film CF 1 is formed also over the bottom surfaces and side walls of the contact holes CT 1 , CT 2 , CT 3 , CT 4 , CT 5 , and CT 6 .
- each of the heaters HT integrally has the heater main body portion HTa and the contact portions CB 5 and CB 6 (see FIG. 31 ).
- the heater HT is made of the patterned conductive film CF 1 .
- the manufacturing process in the present second embodiment is otherwise substantially the same as that in the foregoing first embodiment.
- each of the heaters HT integrally includes the heater main body portion HTa formed over the interlayer insulating film IL 3 and over the optical waveguide WO 3 , the contact portion CB 5 formed in the contact hole CT 5 , and the contact portion CB 6 formed in the contact hole CT 6 . Consequently, in the phase modulation portions PM 2 , the optical waveguides WO 3 are surrounded by the heaters HT. This can improve the function of heating the optical waveguides WO 3 performed by the heaters HT.
- the present second embodiment has the contact portions CB 5 and CB 6 , the two-dimensional size (particularly the size in the Y-direction in each of FIGS. 7 and 33 ) of each of the heaters HT is smaller in the foregoing first embodiment than in the present second embodiment. Accordingly, the two-dimensional size of each of the optical modulators PC 2 can be set smaller in the foregoing first embodiment than in the present second embodiment. Therefore, in terms of reducing the size of the semiconductor device, the foregoing first embodiment is advantageous over the present second embodiment.
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